So how old is Tony's boyfriend supposed to be? I mean how many attractive, sweet, kind, loving grown men are trying to be serious with a high school kid unless they're up to some R. Kelly shenanigans or are a recent graduate and they knew each other before. That's the thing about having grown ass adults playing teenage characters, they look similar in age because the actors probably are, hell Tony looks older than him, so the difference isn't as glaring as it could be in real life.
But we're supposed to think its cute. If it was an older guy with one of the girls, it would be yet another melodramatic plot point.